Oral compositions such as dentifrices generally contain a binding agent such as sodium carboxymethyl cellulose, carrageenan or xantham gum. When such a component is dissolved in water, it becomes viscous and binds a powder component such as an abrasive with a liquid component to realize a shape retention or a suitable viscosity.
Therefore, in water-free oral compositions such as dentifrices, it is difficult to keep the shape retention because of the lack in the viscosity and, as a result, a powdery component is separated from a liquid component in the oral composition with time.
On the other hand, various active ingredients are sometimes contained in the oral compositions such as dentifrices for the purpose of imparting some functions or effects to them. The active ingredients include components for accelerating remineralization (recrystalization), fluorides, sterilizers, anti-inflammatory agents, hemostatics and various enzymes.
The components for accelerating remineralization (recrystalization) include calcium phosphate compounds such as hydroxyapatite. In these compounds, α-tricalcium phosphate (hereinafter referred to as “α-TCP”) is known to exhibit an extremely high effect of accelerating remineralization (recrystalization) in the oral cavity and also to be effective in preventing and repairing tooth decay. However, on the other hand, α-TCP is converted to an apatite compound in the presence of water. This reaction is accelerated in the presence of a fluoride or a water-soluble calcium phosphate to cause a self-curing reaction. Thus, α-TCP could not be stably contained in oral compositions such as ordinary water-containing dentifrices.
The fluorides include sodium fluoride, potassium fluoride, sodium monofluorophosphate, tin fluorides, etc. The effect of the fluorides is that hydroxyapatite of teeth is fluorinated with fluorine ion to improve the quality of the teeth. When a fluoride is contained into an ordinary water-containing oral composition such as a dentifrice, fluorine ion is dissolved in water in the oral composition and then adsorbed on other components such as an abrasive not to develop the exhibition of the essential effect of fluorine ion. For example, it is known that in a water-containing oral composition which also contains a sodium fluoride or a tin fluoride and an abrasive such as calcium phosphate or calcium carbonate, fluorine ion adsorbs on the abrasive to inactivate fluorine ion.
The enzymes include, for example, lysozyme, mutanase, protease, amylase and dextranase. Many of these enzymes have a problem that when such an enzyme is contained into a water-containing composition, it causes the hydrolysis to lower the enzymatic activity. Therefore, when such an enzyme is to be contained into such a water-containing composition, a difficultly decomposable enzyme must be selected or a method for stably incorporating each enzyme must be selected.
Hinokitiol as a natural sterilizer or ε-aminocaproic acid as a hemostatic is contained into an oral composition such as a dentifrice in some cases. However, when such an active ingredient is contained into a water-containing composition, the quantitative values thereof are inclined to be lowered by the hydrolysis. Further, it is known that ascorbic acid and salts thereof are effective on the hemorrhage in cases of gingivitis and periodontitis, etc. However, the decomposition reaction thereof easily proceeds in the presence of water to lower the content of ascorbic acid or a salt thereof and also to cause coloring of the composition.
All the problems of the stability of these active ingredients are caused by water contained in the oral compositions such as dentifrices. Under these conditions, it is demanded to develop a substantially water-free oral composition such as a dentifrice which can stably contain α-TCP, fluorides, enzymes, hinokitiol, ε-aminocaproic acid, ascorbic acid, etc. and which can have a shape-retaining property and wherein the separation of the powdery component from the liquid component with time does not occur.
As bases for the oral composition, which are suitable for substantially water-free or non-aqueous oral composition, for example, bases containing agar or gelatin were proposed in Japanese Patent Unexamined Publication No. 2002-114656; bases containing polyethylene powder or polyethylene wax were proposed in Japanese Patent Unexamined Publication No. 2002-114657; and bases containing polyvinylpyrrolidone were proposed in Japanese Patent Unexamined Publication No. 2002-255772.